To be fair, I wouldn't say we gave them "mountains" of evidence or proof.
We still need hd footage of earth and the other planets that is unedited and is shot well enough to be accepted by anyone who watches it. And I know there will still be some who claim it's cgi, but we still need way better footage of space than what we have now. And it's mainly the editing of the footage they've already shown.
But it should be obvious to them that if the sun and moon are both spheroidal/globular it stands to reason that the earth itself isn't a flat disc.
I think the UN is pushing the FE theory to demonize Abrahamic monotheism myself. :{D